We investigated the activity of irinotecan given with a more convenient modified bimonthly de Gramont regimen of bolus and infusional 5-fluorouracil [IrMdG] in advanced or metastatic colorectal cancer in the first and second line setting. Irinotecan 180 mg m(-2) was infused over 90 min. L-folinic acid 175 mg or d,l folinic acid 350 mg was given over 2 h followed by a bolus of 5-fluorouracil (400 mg m(-2)) and a 46 h continuous infusion of 5-fluorouracil (2.4-2.8 g m(-2)). Forty-six previously untreated patients (Group A) and 36 who had received 5-fluorouracil for metastatic disease (Group B) were recruited. Seventy-eight patients were evaluable for response. A partial response was seen in 13 out of 43 (30% [95%CI 28.1-31.9%]) in Group A and 8/35 (23% [95% CI 17.9-28.1%]) in Group B. 40% (95%CI 38.1-41.9%) of Group A and 26% (95% CI 20.9-31.1%) of Group B patients achieved disease stabilisation. The median progression free survival from the start of this treatment was 7 months (95% CI 4.4-9.6 months) in Group A and 5 months (95% CI 2.8-7.2 months) in Group B. Median overall survival was 14 months (95% CI 9.0-18.9) in Group A and 11 months (95% CI 5.9-16.1) in Group B. Grade 3-4 toxicity in both treatment groups were similar; leucopenia 17% and diarrhoea 7-8%. Grade 3-4 mucositis was not seen and severe alopecia affected only three patients. IrMdG is an active and well-tolerated regimen for both the first and second line treatment of advanced colorectal cancer.